Unit 14/15 Aquatic Ecosystems Lesson Overview Unit 14/15 Aquatic Ecosystems

Aquatic Ecosystems – Condition Underwater - What factors affect life in aquatic ecosystems? Aquatic organisms are affected primarily by: 1. water’s depth 2. temperature 3. currents 4. amount of dissolved nutrients

1. Water Depth - Sunlight penetrates only a relatively short distance through water. photic zone - the sunlit region near the surface in which photosynthesis can occur. The photic zone may be as deep as 200 meters in tropical seas, but just a few meters deep or less in rivers and swamps. Photosynthetic algae, called phytoplankton, live in the photic zone. aphotic zone - below the photic zone is the dark, where photosynthesis cannot occur.

2. Temperature and 3. Currents Aquatic habitats are warmer near the equator and colder near the poles. Temperature in aquatic habitats also often varies with depth. The deepest parts of lakes and oceans are often colder than surface waters. Currents in lakes and oceans can dramatically affect water temperature because they can carry water that is significantly warmer or cooler than would be typical for any given latitude, depth, or distance from shore.

4. Nutrient Availability Organisms need certain substances to live, such as oxygen, nitrogen, potassium, and phosphorus. The type and availability of these dissolved substances vary within and between bodies of water, greatly affecting the types of organisms that can survive there.

Marine Ecosystems Ecologists typically divide the ocean into zones based on depth and distance from shore. Starting with the shallowest and closest to land, marine ecosystems include: the intertidal zone the coastal ocean the open ocean

Marine Ecosystems This diagram shows the different zones in an ocean.

Intertidal Zone Organisms in the intertidal zone are submerged in seawater at high tide and exposed to air and sunlight at low tide. These organisms are subjected to regular and extreme changes in temperature and are often battered by waves and currents. There, barnacles and seaweed permanently attach themselves to the rocks.

Coastal Ocean The coastal ocean extends from the low-tide mark to the outer edge of the continental shelf—the relatively shallow border that surrounds the continents. Water in the coastal ocean is brightly lit, and is often supplied with nutrients by freshwater runoff from land. As a result, coastal oceans tend to be highly productive.

Open Ocean The open ocean begins at the edge of the continental shelf and extends outward. More than 90 percent of the world’s ocean area is considered open ocean. The open ocean is divided into two zones based on light penetration—the photic and aphotic.

The Open Ocean Photic Zone Most of the process of photosynthesis on Earth occurs in the sunlit top 100 meters of the open ocean.

The Open Ocean Aphotic Zone The permanently dark aphotic zone includes the deepest parts of the ocean. Deep ocean organisms, like hatchet fish, are exposed to high pressure, frigid temperatures, and total darkness.

Marine Ecosystems by Zones  

Complete the diagram and shade in everything under the 200m mark to identify the aphotic zone.  

Unit 14/15 Biogeochemical Cycles Lesson Overview Unit 14/15 Biogeochemical Cycles

MATTER CYCLING IN ECOSYSTEMS Nutrient Cycles: Global Recycling Global Cycles recycle nutrients through the earth’s air, land, water, and living organisms. Nutrients are the elements and compounds that organisms need to live, grow, and reproduce. Biogeochemical cycles move these substances through air, water, soil, rock and living organisms.

Sustaining Life on Earth… Biosphere Carbon cycle Phosphorus Nitrogen Water Oxygen Heat in the environment Heat Biogeochemical cycles are driven directly or indirectly by incoming solar energy and gravity.

The Water Cycle Figure 3-26

The Water Cycle 1. Evaporation and Transpiration 2. Condensation 3. Precipitation 4. Ground Infiltration and Percolation 5. Surface Runoff

Effects of Human Activities on Water Cycle We alter the water cycle by: Withdrawing large amounts of freshwater. Clearing vegetation and eroding soils. Polluting surface and underground water. Contributing to climate change.

The Carbon Cycle

The Carbon Cycle

Carbon Cycle (Gaseous Cycle) 1. Photosynthesis Remove CO2 2. Respiration Returns CO2 3. Carbonates and Ocean (1st and 2nd Sink) 4. Fossil fuels trapped CO2 from dead organisms

Effects of Human Activities on Carbon Cycle We alter the carbon cycle by adding excess CO2 to the atmosphere through: Burning fossil fuels. Clearing vegetation faster than it is replaced. Figure 3-28

The Nitrogen Cycle: Bacteria in Action

Nitrogen Cycle Unusable Nitrogen N2 Present in atmosphere 1. Nitrogen Fixation N2 to NH3 (ammonia) by cyanobacteria and Rhizobium 2. Nitrification: Specialized Aerobic bacteria NH3 to toxic NO2- (nitrite) to NO3- (nitrate) for use by plants 3. Assimilation: plant absorbs ammonia, and ammonium ions (NH4-) and nitrate ions 4. Ammonification: Decomposing bacteria convert nitrogen rich compounds to ammonia and ammonium ions 5. Denitrification: Specialized bacteria convert ammonia and ammonium ions to nitrates and nitrites and then back to nitrogen gas and nitrous oxide

Effects of Human Activities on the Nitrogen Cycle We alter the nitrogen cycle by: Adding gases that contribute to acid rain. Adding nitrous oxide to the atmosphere through farming practices which can warm the atmosphere and deplete ozone. Contaminating ground water from nitrate ions in inorganic fertilizers. Releasing nitrogen into the troposphere through deforestation.

Effects of Human Activities on the Nitrogen Cycle Human activities such as production of fertilizers now fix more nitrogen than all natural sources combined. Figure 3-30